Lupus nephropathy is a major cause of disability and death in patients with systemic lupus erythematosus (SLE). No overall attempt has been made to correlate the currently available clinical and serologic parameters with renal biopsy in order to evaluate the course and prognosis of this disorder. Since renal biopsy cannot be done frequently, it is essential to learn whether other parameters, such as those utilized in this study, will accurately reflect the kidney status. It is planned to perform renal biopsy in all newly diagnosed cases of SLE, with or without overt renal disease, provided that adequate renal function and good hemostasis are present. Prior to biopsy and at the time of subsequent ones, routine renal function studies will be done. In addition, serum will be analyzed for the presence of a variety of immunologic and serologic parameters, including antitissue and antinuclear antibodies of varying specificity, classes, complement fixing ability, free DNA, and complement. Specimens will be studied by light and electron microscopy and immunofluorescence. Patients will be treated by current conservative measures, serologic studies will be done at regular intervals, and biopsies repeated when there is a significant change in the renal status.